The most common and most likely answer to this crossword clue is the 7 letter word CATCALL
I've seen this crossword clue in Financial Times
C
A
T
C
A
L
L
More clues leading to the result CATCALL
- Players don’t want this at 6, 20 from jazz fan
- Boo jazz fan beginning to criticise everyone
- Tom’s cry of derision
- Tom’s shout shows disapproval
- Derisive noise from audience upset performance in ring
- Bad act and more or less everybody could make it
- Endlessly hear everything, and express disapproval
- Tom’s shout showing disapproval
- Some barracking unit in mews?
- Boo queen’s visit?
Buddy explains!

The straight part
We know that "shows disapproval" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shows disapproval = catcall.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CATCALL mean?
CATCALL noun- A shout or whistle expressing dislike, especially from a crowd or audience; a jeer, a boo.
- A shout, whistle, or comment of a sexual nature, usually made toward a passing woman.
- A whistle blown by a theatre-goer to express disapproval.
- To make such an exclamation.
- In the Eiffel programming language, a run-time error caused by use of the wrong data type.